Anyways, I got a new pair of shoes about 4 months ago when I started running regularly again. I am running 5 days a week and wonder if and when I need new shoes. How can you tell? And should I get them a few weeks before the run, or just use the shoes I am currently using?
Are you getting any sort of pain in your knees or your joints that you didn't have before? That can be a sign of the shoes breaking down. How worn is the sole of the shoe?
If you think that you do need to replace the shoes, then you should probably do so sooner rather than later because you don't want to wear a brand new pair in time for the big race.
A couple of things you'll want to think about...
First, your midsoles (that's the inside of your shoes, between the insole, which you can pull out, and the outsole, which is the bottom of your shoe) will wear out LONG BEFORE your outsole.
In fact, by the time you notice wear on your outsole, your midsole is almost always LONG GONE.
So, as mentioned above, you should always keep a running total of the miles on your shoes (a cumulative total), and get new shoes around 300-500 miles, depending on your size, your running style, the way your foot strikes the ground etc.
The lighter a person is, the longer shoes will last, in general.
A neutral footstrike (which means you basically land on your foot in a "normal" way) will make your shoes last longer.
If most of your running is on hard surfaces, then your shoes will wear faster.
If you're running 5 days a week, then that means you're running back to back days at least a couple of times a week.
If you run 2 days back to back, you should alternate shoes. That means you've got to have at least 2 pair of shoes. (Lots of runners use 3 or 4 -- or even more -- shoes at a time... but that's more out of our love for shoes than for a real need.)
But it's true... and not just a ploy by the shoe companies... that you need to alternate shoes on consecutive days.
This allows your midsoles to spring back. If you run in the same pair every day, a couple of things happen:
1) The midsoles don't spring back, and therefore you don't have as much cushioning.
2) The shoes don't last as long, because the midsole is ruined faster. You actually get more mileage out of EACH PAIR of shoes if you are alternating them.
Anyway, hope that helps. Have a look at this page (http://www.ordinaryrunner.com/running-shoes.html) for more info on shoes, if you'd like.
Hope those thoughts help some!